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Sega Mega Drive/Genesis Hardware
Sega Mega Drive Motherboard revisions Model 1 VA1 BD M5 VA1 VA2 BD M5 USA VA2 837-6992 VA3 BD M5 USA VA3 837-7071 VA4 BD M5 PAL VA4 VA5 The only difference is the IC4 315-5402 VA6 BD M5 PAL VA6 BD M5 USA VA6 VA6.8 VA7 BD M5 USA VA7 171-6217-11 The VA7 is almost a Genesis 2 PCB in a Genesis 1 case. It even shares the same PCB prefix (PC). Category:Sega Genesis Category:Hardware Model 2 VA0 PAL VA1 BD MD2 VA1 USA VA1 BD MD2 VA1 PAL VA1 BD MD2 VA1 ASIA VA1.8 BD MD2 VA1.8 USA VA1.8 BD MD2 VA1.8 PAL VA1.8 BD MD2 VA1.8 ASIA VA2 BD MD2 VA2 USA This revision, along with the VA2.3, uses a discrete YM2612 FM synthesizer. It is also the first Model 2 to feature the 315-5684 sound network/headphones amplifier. A small daughterboard with a 74HC14 hex-inverting schmitt trigger is typically present, its function is unknown. The BA10358 op-amplifier serves as the FM pre-amplifier. A series resistor at R31 is responsible for the distorted PSG sound reported on these models. Replacing R31 with a 0-ohm jumper fixes the PSG distortion. VA2.3 PC BD MD2 VA2.3 USA This revision integrates the 74HC14 hex-inverting Schmitt trigger, and moves some components around. Most VA2.3s use the 315-5685 main ASIC, but some systems may use the 315-5786 alternatively. The 315-5685 ASIC has slightly broken shadow/highlight support, where the shadow/highlight effects are offset to the right by one pixel onscreen. The 315-5786 ASIC does not have this problem. As with the VA2, a series resistor at R31 causes PSG distortion. Replacing it with a 0-ohm jumper fixes this distortion. VA3 BD MD2 VA3 USA HAL This is the first Model 2 system to utilize a smaller motherboard footprint. It is essentially a much improved VA1.8, using the 315-5684 amplifier first featured on the VA2 and VA2.3 revision motherboards. The PSG distortion problems have been fixed with this revision. This is also the last motherboard revision to feature the NTSC-only Samsung KA2195D encoder. Early VA3 systems may use the older Sony CXA1145M encoder, while most use either the KA2195D or CXA1645M encoders. List of IC's VA4 BD MD2 VA4 Final Model 2 motherboard revision. This system features a 'Genesis-on-a-Chip' (GOAC), which integrates the VDP, FM sound source, 68000 and Z80 CPUs into one chip. First revision Model 3 systems also use this ASIC. It also uses a similar reduced motherboard footprint to the VA3 model. Model 3 VA1 VA2 Notes Most of the time the main SEGA IC's are based on/renamed chips from other brands as follows: *MD1 VA0, VA1, VA2, VA3, VA4, VA5, VA6, VA6.8 : Yamaha YM7101 / FC1001 = Sega 315-5313 / 315-5313A / 315-5313A-01 : Yamaha YM6045 / YM6045C = Sega 315-5308 / 315-5364 : Yamaha YM6046 = Sega 315-5309 *MD1 VA7 & MD2 VA0, VA1, VA1.8, VA3 : Yamaha FC1004 = Sega 315-5487 / 315-5487-01 / 315-5487-10 / 315-5660 / 315-5660-02 / 315-5708 / 315-5708-01 *Sega Nomad & some MD2 VA3's : Yamaha FF1004 = Sega 315-5700 *MD2 VA2, VA2.3 : Toshiba T9N13BF = Sega 315-5786 : Toshiba TC6158AF = Sega 315-5685. This ASIC has slightly broken shadow/highlight support. : Rohm BA6166 = Sega 315-5684 *MD2 VA4 & GEN3 VA1 : Yamaha FJ3002 = Sega 315-5960 *GEN3 VA2 : Yamaha FQ8007 = Sega 315-6123 See Also *Sega Genesis *Sega Genesis Cartridge Category:Sega Genesis Category:Hardware